The present invention relates to an inflator for inflating an inflatable vehicle occupant protection device, such as an air bag. More particularly, the present invention relates to an inflator having a variable output.
It is known to inflate an inflatable vehicle occupant protection device to help protect a vehicle occupant. The protection device is inflated by inflation fluid from an inflator. One particular type of inflatable vehicle occupant protection device is an air bag that may be steering wheel mounted or dash mounted. Upon the occurrence of an event for which occupant protection is desired, the air bags are inflated into a position between an occupant of the vehicle and the vehicle steering wheel and/or dash to help protect the vehicle occupant.
It is known to tailor the flow rate of the inflation fluid provided by an inflator in order to inflate an inflatable vehicle occupant protection device in a predetermined manner. For example, it is known to vary the pressure to which the inflatable vehicle occupant protection device is inflated in accordance with factors such as crash severity and the size, weight, and/or position of the occupant. Also, it is known to vary inflation fluid flow rate to help control the rate at which an inflatable vehicle occupant protection device is inflated and to help control the length of time that the device remains inflated. Known inflators accomplish this through the use of one or more ignitable pyrotechnic charges that can burn for predetermined periods of time and/or in a predetermined sequence.
An apparatus includes an inflatable vehicle occupant protection device and an inflation fluid source for providing inflation fluid for inflating the protection device. The apparatus also includes an opening through which the inflation fluid flows from the inflation fluid source. A member is movable to control flow of the inflation fluid through the opening. A volume of a field responsive fluid resists movement of the member. The field responsive fluid has a viscosity that varies in response to an energy field acting on the fluid. The apparatus further includes means for varying the viscosity of the field responsive fluid to vary the resistance to movement of the member.